Oil smarts: A guide to picking the best one for your car

Ricky Gonzalez changes the oil in a car at Hilltop Service Station in Seattle. (Barry Gibbons / Special to NWautos)

Old oil pours from a car during an oil change at Hilltop Service Station on Capitol Hill in Seattle. (Barry Gibbons / Special to NWautos)

Without oil to lubricate its many quick-moving metal parts, a car's engine eventually will wear down and literally grind to a halt. With more choices than ever on the market, here's a quick look at the benefits of the most common.

Conventional motor oil, also called mineral oil, is refined from crude oil, with additives to protect against deterioration under extreme weather conditions. It remains the best choice for most motorists with a typical daily commute, given that most cars are engineered to run on conventional oil, says Mike Allen, senior automotive editor of Popular Mechanics magazine.
Synthetic motor oil is made from chemically modified petroleum components or from other raw materials. It is designed to handle extreme temperatures better than conventional oil, reducing wear for a cleaner-running engine.

Synthetic oil is more expensive than conventional, but offers higher performance. Allen recommends it for drivers with sports cars, race cars and other high-performance vehicles; those who live in extremely hot or cold climates; and those whose vehicles tow large trailers and generate high-engine temperatures.

Synthetic blends are just that: a mix of conventional and synthetic motor oils to produce a cost-effective happy medium.

Re-refined or recycled motor oil is used oil that has undergone an extensive re-refining process to remove contaminants so that it can safely be used again. Re-refined oil certified by the American Petroleum Institute (API) must undergo the same testing and meet the same standards as lubricants made from virgin crude.

Where to recycle used motor oil

Used motor oil is highly toxic to the environment. Many hazardous-waste facilities and private businesses accept used oil (be sure to transfer it to a sealed container). Visit King County's Local Hazardous Waste Management Program website to find a nearby location: lhwmp.org/home/HHW/motor-oil.aspx.

Many government and private fleets have used re-refined or recycled oil for years. More automakers are now allowing their use under warranty, and the state of California strongly encourages its use as an environmentally friendly choice. Re-refined oil sometimes is cheaper than conventional motor oil, "but not cheaper in quality," says Dave Armstrong, fleet manager for AAA Washington and a National Institute for Automotive Service Excellence (ASE)-certified master technician.

Both experts agree that regular oil changes are just as important as selecting the best oil for your car and driving style, and maybe even more critical to engine performance and life.

"Most people do not need better oil; they need to change their oil at more regular intervals," Allen says. With its extra-long lifespan, synthetic oil often prompts drivers to put off oil changes indefinitely. While the oil itself may remain functional after thousands of miles, it's likely contaminated with carbon, unburned fuel, partially burned fuel, water and acids, he says.

"You change your oil not because you need to put better oil in," Allen says. "You change it to remove the contaminants that are being circulated in the old oil."

Ultimately, your car's owner's manual contains the best advice. Automakers have done an enormous amount of research to ensure that their cars, with proper maintenance, will go the distance, Armstrong and Allen say.

"If [drivers] follow the oil-change and viscosity-grade recommendations in the owner's manual," Allen says, "their engine will last 200,000 miles."